Flame deflector for a water heater pilot burner

ABSTRACT

A gas-fired water heater includes a pilot assembly that provides a pilot flame deflector. The pilot flame deflector causes the pilot flame to surround a hot junctions end of a thermopile. The flame deflector does not cover a cold junctions end of the thermopile, such that the cold junctions are ventilated. A temperature differential between the hot and cold junctions is increase by ventilating the cold junctions and surrounding the hot junctions with the pilot flame. The temperature differential is further increased by radiant and convective heat applied to the hot junctions as a result of the flame deflector.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. 119(e) of the filing date of U.S. Provisional Application No. 61/480,476, filed Apr. 29, 2011, the entire contents of which are incorporated herein by reference.

BACKGROUND

The present invention relates to water heaters, and more particularly to pilot burners for water heaters.

SUMMARY

The invention provides a pilot assembly for use with a water heater, the pilot assembly comprising: a pilot burner operable to burn a fuel-air mixture to create a pilot flame; a thermopile including a plurality of thermocouples, each thermocouple including a hot junction spaced apart from a cold junction; and a flame deflector positioned near the hot junctions; wherein the pilot flame is directed toward the hot junctions; wherein the flame deflector causes the pilot flame to contact the thermopile near the hot junctions around at least 270 degrees of a circumference of the thermopile; and wherein the flame deflector does not cover the cold junctions of the thermopile, such that the cold junctions are ventilated to increase a temperature differential between the hot junctions and the cold junctions.

In some embodiments, the flame deflector directs radiant energy and convective heat energy from the pilot flame toward the hot junctions. In some embodiments, the flame deflector causes the pilot flame to contact the thermopile near the hot junctions around 360 degrees of the circumference of the thermopile. In some embodiments, the flame deflector extends from a base to a distal end and the distal end includes a downwardly directed tab. In some embodiments, a gap is defined between the flame deflector and the thermopile such that the pilot flame fills the gap and contacts both the flame deflector and the thermopile.

The invention also provides a method of retrofitting a gas-fired water heater having a pilot burner and a thermopile having hot junctions and cold junctions, the thermopile generating sufficient energy to open a supply valve to supply gaseous fuel to the pilot burner when a temperature differential between the hot junctions and cold junctions is at least at pilot burner threshold temperature differential, the method comprising the steps of: (a) installing a pilot flame deflector over the hot junctions; (b) deflecting the pilot flame with the flame deflector such that the pilot flame covers at least 270 degrees of the hot junctions; (c) avoiding positioning the flame deflector over the cold junctions such that the cold junctions are ventilated and such that the temperature differential between the hot junctions and cold junctions is enhanced; and (d) achieving the pilot burner threshold temperature differential with less gas consumption compared to the water heater prior to installing the pilot flame deflector.

In some embodiments, step (b) includes covering 360 degrees of the hot junctions with the pilot flame. In some embodiments, the pilot burner includes an original pilot burner orifice through which gaseous fuel flows for the pilot flame; the method further comprising the step of removing the original pilot burner and installing a replacement pilot burner having a smaller-diameter orifice than the original pilot burner orifice.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a gas-fired water heater embodying the present invention.

FIG. 2 is a tube-door assembly for use with the water heater.

FIG. 3 is an end view of the tube-door assembly.

FIG. 4 is an exploded view of a thermopile used in the tube-door assembly.

FIG. 5 is a top view the tube-door assembly.

FIG. 6 illustrates a tube-door assembly that does not include the flame deflector of the present invention.

Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.

DETAILED DESCRIPTION

FIG. 1 illustrates a water heater 10 that includes a base pan or base ring 12, a storage tank 15, and an insulating jacket 20. The storage tank 15 is supported by a skirt 25 that partially defines a combustion chamber 30 below the storage tank 15. The base ring 12 supports the skirt 25 and storage tank 15, and includes air inlets 27 for the inflow of combustion air into the combustion chamber 30. A flue 35 extends from the combustion chamber 30 through the water in the storage tank 15, and out a top of the storage tank 15. A cold water inlet spud 40 and a hot water outlet spud 45 are mounted around holes in the top of the storage tank 15 for the respective provision of cold water to the storage tank 15 and removal of hot water from the storage tank 15 during performance draws. The water heater 10 may also include a sacrificial anode 51 to protect the tank 15 walls from corrosion or reduce the rate at which such walls may corrode or rust. A gas valve 50 is connected to a supply of gaseous fuel such as natural gas or propane. A portion of a tube-door assembly 100 is secured to the jacket 20 of the water heater 10 and a portion extends into the combustion chamber 30.

FIGS. 2 and 3 illustrate the tube-door assembly 100, which includes a door 105, a main burner 110, a gas supply line 113, a main burner tube 115, an air duct 120, and a pilot assembly 125. The gas supply line 113 and main burner tube 115 are coupled in-line. More specifically, the main burner tube 115 extends through a hole in the door 105, and an end of the gas supply line 113 is received around the end of the burner tube 115 outside the door 105. The tube junction is crimped (as with a crimp ring, for example) or otherwise joined to create a gas-tight interconnection between the gas supply line 113 and the burner tube 115. The tube junction is gas-tightly interconnected with the door 105 to avoid ingress or egress of air and flammable vapors through the hole that accommodates the tube junction. The gas supply line 113 communicates with the gas valve 50 for selective flow of gaseous fuel as needed to heat the water in the tank 15. The gaseous fuel flows from the gas supply line 113 to the main burner tube 115 and ultimately to the main burner 110 where it is mixed with air and combusted.

The pilot assembly 125 includes a pilot burner 130, an igniter 135, a thermopile 140, a flame deflector 145, and a mounting bracket 150. In other constructions, the air duct 120 is not included. A pilot burner tube 155 supplies the gaseous fuel to the pilot burner 130. The pilot burner tube 155 passes gas-tightly through the door 105.

Referring now to FIG. 3, fuel exits the pilot burner 130 through an orifice 160, mixes with the air near the pilot burner 130. The igniter 135 generates a spark to ignite the resulting fuel-air mixture, which creates a pilot flame 165.

Referring now to FIG. 4, the thermopile 140 includes a base 167, a shell 168, and a plurality of thermocouples 170. The cross-section of the thermopile 140 is circular. Each thermocouple 170 includes a first end 180 and a second end 190. The first ends 180 of adjacent thermocouples 170 are joined to define hot junctions 175, and the second ends 190 are joined to define cold junctions 185. The thermopile 140 is assembled by inserting the cold junctions 185 in the base 167 and sliding the shell 168 over the hot junctions 175 of the thermopile 140. The shell 168 is connected to the base 167 so that the thermopile 140 is contained in the space defined between the shell 168 and the base 167. The temperature differential between the hot junctions 175 and the cold junctions 185 generates a voltage that is proportional to the temperature differential.

Referring again to FIGS. 2 and 3, the thermopile 140 is supported by the mounting bracket 150 and positioned so that the hot junctions 175 are positioned across from the orifice 160 and the pilot flame 165 is directed toward the hot junctions 175. The flame deflector 145 is also supported by the mounting bracket 150 and extends near the hot junctions 175 so that a gap 195 is formed between the thermopile 140 and the flame deflector 145.

A control wire 200 communicates between the thermopile 140 and the gas valve 50, and transmits the voltage from the thermopile 140 to a controller or solenoid valve in the gas valve 50. When the voltage is equal to or above a pilot burner threshold voltage (i.e., when the temperature differential between the hot and cold junctions 175, 185 is equal to or above a pilot burner threshold temperature differential), the gas valve 50 supplies gas to the pilot burner 130. When the voltage is equal to or above a main burner threshold voltage (i.e., when the temperature differential between the hot and cold junctions 175, 185 is equal to or above a main burner threshold temperature differential), the gas valve 50 is able to supply gas to the main burner 130.

At the main burner threshold temperature differential, the thermopile 140 generates sufficient power to operate a main burner valve of the gas valve 50. When there is a call for heat and the main burner threshold temperature differential is met, a control algorithm will complete the electrical circuit to the main burner valve and power from the thermopile 140 will open the main burner gas valve to allow fuel to flow to the main burner 110. The pilot flame 165 will ignite the fuel-air mixture exiting from the main burner 110 to complete the main burner ignition sequence. When a water temperature set point for the water in the storage tank 15 is satisfied, the control algorithm will disconnect the electrical circuit to the main gas valve 50, causing the main burner valve to close and the main burner 110 to extinguish. The pilot flame 165 will remain lit in anticipation of the next heating cycle.

If the pilot flame 165 is extinguished, the temperature differential between the hot junctions 175 and the cold junctions 185 will decrease below the pilot burner threshold temperature differential. This causes the voltage of the thermopile 140 to decrease and closes the pilot valve to prevent fuel flow to the pilot burner 130 and the main burner 110. This is a safety feature but may create nuisances when the energy of the pilot flame 165 is not sufficient or consistent enough to generate and maintain the pilot burner threshold temperature differential. In these nuisance situations, the pilot flame 165 is lit, but the temperature differential is below the pilot burner threshold temperature differential. For example, this can occur at high altitude, for heaters operating in heavy condensation environments (cold water intake during the winter/spring time or geographical regions with cold water intake). The heavy condensation inside of the combustion chamber will partial cover the air intake (flame arrestor) with water and will restrict the combustion air required to sustain the combustion, or under a lint, dust, oil (LDO) condition where the screen that allows air to enter the combustion chamber is clogged.

The flame deflector, installed over the pilot, protects the pilot flame against the water drops that may quench the pilot flame, protecting in the same time the thermopile hot junctions against quenching or heat lost due to water drops caused by condensation. The 225 surface will confer the protection due to heavy condensation.

“Above,” “below,” and other directional terms are relative and refer to the relationship between the components when used in a water heater in a standard operating position such that the products of combustion flow in the upward direction.

Referring to FIG. 5, the flame deflector 145 includes a base 205, an arm 210, and a tab 215. The base 205 is fastened to the mounting bracket 150. The arm 210 extends from the base 205 and includes a contact portion 225.

The thermopile 140 extends to a distal end 235, which includes the hot junctions 175. The contact portion 225 may be said to be the distal end of the flame deflector 145. The contact portion 225 is positioned above the hot junctions 175 of the thermopile 140. It may therefore be said that the distal end 225 of the flame deflector 145 is positioned over the distal end 235 of the thermopile 140, and the flame deflector 145 does not extend past the distal end 235 of the thermopile 140. In other constructions, the flame deflector 145 may extend past the distal end 235, but such arrangements do not appear to improve the effectiveness of the thermopile 140.

The tab 215 extends downwardly from the contact portion 225. The angle between the tab 215 and the contact portion 225 can vary, but is preferably one-hundred fifty degrees. The size of the tab 215 can also vary. The tab 215 is positioned opposite from the pilot burner 130 so that the thermopile 140 is between the orifice 160 and the tab 215. The tab 215 increases the contact area between the pilot flame 165 and the flame deflector 145 and also helps to achieve three-hundred sixty degrees of contact between the pilot flame 165 and the thermopile 140. The 215 tab will direct the flame down helping to wrap the thermopile hot junction area in the flame envelope. The tab 215 also directs radiant and convective energy from the pilot flame 165 towards the hot junctions 175. In some embodiments, the tab 215 is not included. In other embodiments, the flame deflector 145 has a different shape than shown in the drawings. For example, the contact portion 225 and the tab 215 could be a continuous surface that is downwardly curved toward the thermopile 140.

FIG. 6 illustrates a similar pilot assembly 325 without a flame deflector 145. In this assembly 325, the pilot flame 165 contacts between one-hundred eighty degrees and two-hundred seventy degrees of the circumference of the thermopile 140.

Returning to FIG. 3, in an arrangement according to the present invention, pilot flame 165 contacts the flame deflector 145 and fills the gap 195, causing the pilot flame 165 to envelop the thermopile 140 at the hot junctions 175. Under most operating conditions, the pilot flame 165 contacts the thermopile 140 around three-hundred sixty degrees of the circumference of the hot junctions 175. Under all operating conditions, the pilot flame 165 contacts the thermopile 140 around at least two-hundred seventy degrees of the circumference of the thermopile 140.

Compared to the arrangement 325 that does not include the flame deflector 145, the pilot assembly 125 with the flame deflector 145 increases the contact area between the pilot flame 165 and the thermopile 140. The pilot assembly 125 thereby directly exposes more of the hot junctions 175 to the pilot flame 165 than are directly exposed in the pilot assembly 325 without a flame deflector 145 (e.g., as illustrated in FIG. 6). This increases the amount of pilot flame energy delivered to the hot junctions 175 relative to the pilot assembly 325 without a flame deflector 145. Additionally, the flame deflector 145 directs a portion of the radiant energy and convective heat energy from the pilot flame 165 toward the hot junctions 175. The arrangement 325 does not resist quenching as a result of condensation water dropping on the burner, pilot flame, and thermopile hot junction area. This effect (condensation) can create field nuisances dropping out the pilot and stopping the water heater operation in the arrangement 325.

As seen in FIG. 5, the flame deflector 145 extends from the bracket 150 and an angle θ of 44° in the illustrated embodiment. This gives rise to a generally triangular window 250 between the flame deflector 145 and the burner 110 over the cold junctions 185 of the thermopile 140. No portion of the flame deflector 145 is positioned above the cold junctions 185. This allows the air in the combustion chamber to freely circulate around the thermopile 140 near the cold junctions 185, thereby ventilating the cold junctions 185. The shape and position of the flame deflector 145 therefore allow the cold junctions 185 of the thermopile 140 to remain relatively cold compared to the hot junctions 175.

By increasing the energy (flame, radiant, and convective) delivered to the hot junctions 175 and allowing the cold junctions 185 to be ventilated, the flame deflector 145 increases the effectiveness of the thermopile 140 by increasing the temperature differential between the hot junctions 175 and the cold junctions 185, when compared to a pilot assembly 325 (FIG. 6) that does not include the flame deflector 145 or when compared to a pilot assembly that includes a flame deflector but which does not provide a window (such as window 250) over the cold junctions 185. This helps to achieve the pilot burner threshold temperature differential across a variety of operating conditions, including different fuels (i.e. natural gas and LP gas), different air pressures, different fuel pressures, and different fuel-air ratios.

In air-lean operating conditions, the pilot flame 165 becomes longer and has a relatively large dead-zone in which combustion is not occurring, which results in relatively low temperatures at the hot junctions 175 even when the pilot flame 165 is burning. In air-lean operating conditions, the pilot flame is a soft floating flame looking for air to complete the combustion. The floating pilot flame in arrangements 325 will direct to situations when the flame is not in contact with the thermopile hot junction for a limited time causing voltage fluctuation. The thermopile voltage fluctuation may have low values where the voltages become close to minimum threshold voltage required for the system to operate. The flame deflector will shape the flame, forcing the flame to be kept on the thermopile hot junction area, even in air-lean operation conditions getting a more constant voltage to the system. By increasing the contact area between the pilot flame 165 and the circumference of the thermopile 140 and by directing a portion of the radiant energy and convective heat energy from the pilot flame 165 toward the hot junctions 175, the flame deflector 145 increases the temperature of the hot junctions 175 relative to the pilot assembly 325 (FIG. 6) without the flame deflector 145 at a similar air-lean operating condition. Air-lean operating conditions include high altitude use (at or above five thousand feet above sea level) and operation a lint, dust, oil (LDO) condition.

The increased thermopile effectiveness of the pilot assembly 125 provides opportunities to improve the efficiency of the water heater. The pilot assembly 125 with the flame deflector 145 allows a pilot burner 130 with a smaller diameter orifice 160 to perform similar to or better than the pilot assembly 325 (FIG. 6) without the flame deflector 145, or with a pilot burner 130 having a larger diameter orifice 160.

The smaller orifice 160 size results in less fuel being used by the pilot burner 130. For example, tests were conducted using a pilot assembly 125 including the flame deflector 145 and having a pilot burner 130 with a 0.012 inch diameter orifice 160 and a pilot assembly 325 without the flame deflector 145 and using a pilot burner 130 with a 0.014 inch diameter orifice 160. As tested, the smaller orifice size saved an average of 3.3 cubic feet of fuel over twenty-four hours of operation time and increased the water heater efficiency by about two percent without any diminution or change in performance of the water heater.

Additionally, the flame deflector 145 protects the pilot flame 165 and the thermopile 140 from condensation that may drip from the bottom of the storage tank onto the pilot flame 165 or the thermopile 140. Without the flame deflector 145, this condensation could extinguish the pilot flame 165 or reduce the temperature at the hot junctions 175. Similarly, the flame deflector 145 protects the pilot flame 165 from down drafts that may blow through the flue to the combustion chamber.

In an alternative use, the flame deflector 145 can be used to retrofit an existing water heater. A retrofit kit including a flame deflector 145 and a pilot burner having a smaller diameter orifice than the pilot burner in the existing water heater would allow a user to improve the efficiency of an existing water heater.

Various features of the invention are set forth in the following claims. 

1. A pilot assembly for use with a water heater, the pilot assembly comprising: a pilot burner operable to burn a fuel-air mixture to create a pilot flame; a thermopile including a plurality of thermocouples, each thermocouple including a hot junction spaced apart from a cold junction; and a flame deflector positioned near the hot junctions; wherein the pilot flame is directed toward the hot junctions; wherein the flame deflector causes the pilot flame to contact the thermopile near the hot junctions around at least 270 degrees of a circumference of the thermopile; and wherein the flame deflector does not cover the cold junctions of the thermopile, such that the cold junctions are ventilated to increase a temperature differential between the hot junctions and the cold junctions.
 2. The pilot assembly of claim 1, wherein the flame deflector directs radiant energy and convective heat energy from the pilot flame toward the hot junctions.
 3. The pilot assembly of claim 1, wherein the flame deflector causes the pilot flame to contact the thermopile near the hot junctions around 360 degrees of the circumference of the thermopile.
 4. The pilot assembly of claim 1, wherein the flame deflector extends from a base to a distal end and the distal end includes a downwardly directed tab.
 5. The pilot assembly of claim 1, wherein a gap is defined between the flame deflector and the thermopile such that the pilot flame fills the gap and contacts both the flame deflector and the thermopile.
 6. A method of retrofitting a gas-fired water heater having a pilot burner and a thermopile having hot junctions and cold junctions, the thermopile generating sufficient energy to open a supply valve to supply gaseous fuel to the pilot burner when a temperature differential between the hot junctions and cold junctions is at least at pilot burner threshold temperature differential, the method comprising the steps of: (a) installing a pilot flame deflector over the hot junctions; (b) deflecting the pilot flame with the flame deflector such that the pilot flame covers at least 270 degrees of the hot junctions; (c) avoiding positioning the flame deflector over the cold junctions such that the cold junctions are ventilated and such that the temperature differential between the hot junctions and cold junctions is enhanced; and (d) achieving the pilot burner threshold temperature differential with less gas consumption compared to the water heater prior to installing the pilot flame deflector.
 7. The method of claim 6, wherein step (b) includes covering 360 degrees of the hot junctions with the pilot flame.
 8. The method of claim 6, wherein the pilot burner includes an original pilot burner orifice through which gaseous fuel flows for the pilot flame; the method further comprising the step of removing the original pilot burner and installing a replacement pilot burner having a smaller-diameter orifice than the original pilot burner orifice. 